Xenopus death‐domain‐containing proteins FADD and RIP1 synergistically activate JNK and NF‐κB

Abstract

Background information. Death receptors (DRs) induce intracellular signalling upon engagement of their cognate ligands, leading to apoptosis, cell survival or pro-inflammatory responses. In mammals, DR signalling is mediated by the recruitment of several DD (death domain)-containing molecules, such as FADD (Fas-associated DD) and RIP1 (receptor-interacting protein 1).Results. To elucidate the molecular mechanisms of intracellular DR signalling in Xenopus, we have isolated cDNAs encoding xFADD (Xenopus FADD), and xRIP1 and its short isoform xRIP1β, which is produced by alternative splicing of the xRIP1 gene. These DD-containing proteins interacted with Xenopus DR members xDR-M1 and xDR-M2 through their DDs in co-transfected HEK-293T cells. Overexpression of xFADD activated not only xCaspase 8, but also AP-1 (activator protein 1), which reflects activation of JNK (c-Jun N-terminal kinase) and NF-κB (nuclear factor κB). A comparative analysis of xRIP1, a kinase-dead mutant of xRIP1 and xRIP1β indicated that the kinase activity of xRIP1 was required for the activation of AP-1 and NF-κB. Interestingly, xFADD and xRIP1 interacted with each other via their DDs, and the expression of a mutant xRIP1 containing only the DD (xRIP1-DD) repressed the xFADD-induced activation of NF-κB and AP-1. xFADD and xRIP1 synergistically induced the activation of AP-1 and NF-κB, both of which were partially mediated by TRAF2 (tumour-necrosis-factor-receptor-associated factor 2) and TAK1 (transforming-growth-factor-β-activated kinase 1). We also found that the activation pathways of NF-κB induced by xDR-M2 were inhibited by xRIP1-DD.Conclusions. Xenopus FADD, RIP1 and its splice variant RIP1β have been characterized. Interaction of xFADD and xRIP1 induced synergistic activation of JNK and NF-κB. In addition, the NF-κB activation induced by xDR-M2 was partially mediated by xRIP1.

Antigen-Receptor Signaling to Nuclear Factor κB

“…Nevertheless, TAK1 was clearly shown to be required for TCRinduced NF-kB activation in naïve T cells and thymocytes (Liu et al, 2006;Sato et al, 2006;Wan et al, 2006). TRAF2 catalyzes RIP1 K63 polyubiquitination, and RIP1 could in turn associate with the TAK1 complex or with the FADD-caspase 8 complex and thereby activate NF-kB (Ishizawa et al, 2006;Su et al, 2005). Thus, the FADD-caspase 8 complex may bridge the CBM signalosome and IKKa-IKKb and thereby allow phosphorylation of the IKK complex through RIP1 (Figure 3).…”

Tumor necrosis factor–related apoptosis-inducing ligand 1 (TRAIL1) enhances the transition of red blood cells from the larval to adult type during metamorphosis in Xenopus

“…pCI-xDR-M1-Myc-His, pCI-xDR-M2-Myc-His, pCI-xDR-M1-LBR-Myc-His, pCI-xDR-M2-LBR-Myc-His, pcDNA3 His-S-xFADD-DD, and pcDNA3 FLAG-EGFP were described previously. 24,27 Reverse transcription-PCR Total RNA was isolated from X laevis tissues using an RNeasy Mini Kit (QIAGEN). The RNA (1 g) was reverse transcribed with PowerScript (BD Biosciences), according to the manufacturer's instructions.…”

Gradient Descent Optimization in Gene Regulatory Pathways

“…The existance of the optimal pathway through the genes TNF, TNFR1, TRADD and FADD has been observed in [44]–[46]. From FADD, the path obtained by our present method coincides with the intrinsic and the extrinsic pathway and not the path obtained by extreme pathway analysis.…”